1. Field of the Invention
This invention relates to a novel cyclohexane derivative and a liquid crystal composition containing the same.
2. Description of the Prior Art
Liquid crystal display elements utilize the optical anisotropy and the dielectric anisotropy of liquid crystal substances, and there are various modes such as those of T-N (twisted nematic) type, DS (dynamic scattering) type, guest-host type, DAP type, etc., depending on their display mode. The properties required for liquid crystal substances vary according to these modes, but it has been required in common that the substances exhibit liquid crystal phases within a temperature range as broad as possible and also they are stable to moisture, heat, light, air, etc.
At present, however, there is no single compound which satisfies all such requirements; hence liquid crystal compositions obtained by blending several kinds of liquid crystal compounds or blending these with compounds similar to liquid crystals have been used.
As examples of compounds having a 3,4-dihalogenophenyl group or a 3-halogeno-4-cyanophenyl group, Japanese patent application laid-open Nos. Sho 58-83665/ 1983, Sho 58-210057/1983, Sho 59-170042/1984, Sho 59-1984, Sho 59-80651/1984 and Sho 60-45549/1985 disclose respectively ester compounds expressed by the following formulas (1)-(6): ##STR2##
In the above formulas, R represents a linear chain alkyl group.
The compounds of the above formulas are liquid crystal compounds or compounds similar thereto, capable of being used as liquid crystal compositions by blending them with other liquid crystal compounds. The respective compounds of the above formulas, however, have drawbacks as described below. The compounds of the formulas (1), (2) and (3) constitute a liquid crystal blend having a relatively large dielectric anisotropy value (.DELTA..epsilon.), but the blend has a high viscosity, and further among these compounds, there are few which exhibit liquid crystal phases. Compounds expressed by the formulas (4), (5) and (6) have a relatively large dielectric anisotropy value and a suitable mesomorphic range, but they have a high viscosity.
15 Further, since the compounds (1)-(6) have an ester bond, they are liable to be hydrolyzed; thus liquid crystal compositions using these compounds could not have completely solved problems of stability, reliability, etc.